scholarly journals Reticulon-3 Promotes Endosome Maturation at ER Membrane Contact Sites

2021 ◽  
Vol 56 (1) ◽  
pp. 52-66.e7
Author(s):  
Haoxi Wu ◽  
Gia K. Voeltz
Keyword(s):  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact ◽  
Endosome Maturation ◽  
Er Membrane

scholarly journals Calcium signaling at ER membrane contact sites

2015 ◽  
Vol 1853 (9) ◽  
pp. 2012-2017 ◽  
Author(s):  
Thomas Burgoyne ◽  
Sandip Patel ◽  
Emily R. Eden
Keyword(s):  
Calcium Signaling ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact ◽  
Er Membrane

scholarly journals Endoplasmic reticulum–endosome contact increases as endosomes traffic and mature

2013 ◽  
Vol 24 (7) ◽  
pp. 1030-1040 ◽  
Author(s):  
Jonathan R. Friedman ◽  
Jared R. DiBenedetto ◽  
Matthew West ◽  
Ashley A. Rowland ◽  
Gia K. Voeltz
Keyword(s):  
Endoplasmic Reticulum ◽  
Three Dimensional ◽  
Animal Cells ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Major Implication ◽  
Physical Attributes ◽  
Membrane Contact ◽  
Endosomal Pathway ◽  
Endosome Maturation

The endosomal pathway is responsible for plasma membrane cargo uptake, sorting, and, in many cases, lysosome targeting. Endosome maturation is complex, requiring proper spatiotemporal recruitment of factors that regulate the size, maturity, and positioning of endosomal compartments. In animal cells, it also requires trafficking of endosomes on microtubules. Recent work has revealed the presence of contact sites between some endosomes and the endoplasmic reticulum (ER). Although these contact sites are believed to have multiple functions, the frequency, dynamics, and physical attributes of these contacts are poorly understood. Here we use high-resolution three-dimensional electron microscopy to reveal that ER tubules wrap around endosomes and find that both organelles contact microtubules at or near membrane contact sites. As endosomes traffic, they remain bound to the ER, which causes the tubular ER to rearrange its structure around dynamic endosomes at contact sites. Finally, as endosomes transition through steps of maturation, they become more tightly associated with the ER. The major implication of these results is that endosomes mature and traffic while coupled to the ER membrane rather than in isolation.

scholarly journals Endoplasmic Reticulum‐Plasma Membrane Contact Sites as an Organizing Principle for Compartmentalized Calcium and cAMP Signaling

2021 ◽  
Vol 22 (9) ◽  
pp. 4703
Author(s):  
Tim Crul ◽  
József Maléth
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Second Messengers ◽  
Adenosine Monophosphate ◽  
Camp Signaling ◽  
Cell Physiology ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact ◽  
Er Membrane

In eukaryotic cells, ultimate specificity in activation and action—for example, by means of second messengers—of the myriad of signaling cascades is primordial. In fact, versatile and ubiquitous second messengers, such as calcium (Ca2+) and cyclic adenosine monophosphate (cAMP), regulate multiple—sometimes opposite—cellular functions in a specific spatiotemporal manner. Cells achieve this through segregation of the initiators and modulators to specific plasma membrane (PM) subdomains, such as lipid rafts and caveolae, as well as by dynamic close contacts between the endoplasmic reticulum (ER) membrane and other intracellular organelles, including the PM. Especially, these membrane contact sites (MCSs) are currently receiving a lot of attention as their large influence on cell signaling regulation and cell physiology is increasingly appreciated. Depletion of ER Ca2+ stores activates ER membrane STIM proteins, which activate PM-residing Orai and TRPC Ca2+ channels at ER–PM contact sites. Within the MCS, Ca2+ fluxes relay to cAMP signaling through highly interconnected networks. However, the precise mechanisms of MCS formation and the influence of their dynamic lipid environment on their functional maintenance are not completely understood. The current review aims to provide an overview of our current understanding and to identify open questions of the field.

scholarly journals Here, there, and everywhere: The importance of ER membrane contact sites

Science ◽  
2018 ◽  
Vol 361 (6401) ◽  
pp. eaan5835 ◽  
Author(s):  
Haoxi Wu ◽  
Pedro Carvalho ◽  
Gia K. Voeltz
Keyword(s):  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact ◽  
Er Membrane

scholarly journals Pex30-like proteins function as adaptors at distinct ER membrane contact sites

2021 ◽  
Vol 220 (10) ◽  
Author(s):  
Joana Veríssimo Ferreira ◽  
Pedro Carvalho
Keyword(s):  
Lipid Droplets ◽  
De Novo ◽  
Membrane Lipids ◽  
Family Members ◽  
Membrane Curvature ◽  
Organelle Biogenesis ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact ◽  
Er Membrane

Membrane lipids and proteins synthesized in the ER are used for de novo assembly of organelles, such as lipid droplets and peroxisomes. After assembly, the growth of these organelles is supported by ER-derived lipids transferred at membrane contact sites (MCSs). How ER sites for organelle biogenesis and lipid transfer are established and regulated is unclear. Here, we investigate how the ER membrane protein Pex30 and its family members Pex28, Pex29, Pex31, and Pex32 target and function at multiple MCSs. We show that different Pex30 complexes function at distinct ER domains and MCSs. Pex30 targets ER–peroxisome MCSs when bound to Pex28 and Pex32, organizes the nuclear–vacuolar junction when bound to Pex29, and promotes the biogenesis of lipid droplets independently of other family members. Importantly, the reticulon homology domain (RHD) mediates the assembly of the various Pex30 complexes. Given the role of RHD in membrane shaping, our findings offer a mechanistic link between MCS and regulation of membrane curvature.

scholarly journals Protrudin and PDZD8 contribute to neuronal integrity by promoting lipid extraction required for endosome maturation

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Michiko Shirane ◽  
Mariko Wada ◽  
Keiko Morita ◽  
Nahoki Hayashi ◽  
Reina Kunimatsu ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Hela Cells ◽  
Lipid Extraction ◽  
Neuronal Polarity ◽  
Primary Neurons ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact ◽  
Endosome Maturation

Abstract Endosome maturation depends on membrane contact sites (MCSs) formed between endoplasmic reticulum (ER) and endolysosomes (LyLEs). The mechanism underlying lipid supply for this process and its pathophysiological relevance remains unclear, however. Here, we identify PDZD8—the mammalian ortholog of a yeast ERMES subunit—as a protein that interacts with protrudin, which is located at ER-LyLE MCSs. Protrudin and PDZD8 promote the formation of ER-LyLE MCSs, and PDZD8 shows the ability to extract various lipids from the ER. Overexpression of both protrudin and PDZD8 in HeLa cells, as well as their depletion in mouse primary neurons, impairs endosomal homeostasis by inducing the formation of abnormal large vacuoles reminiscent of those apparent in spastin- or REEP1-deficient neurons. The protrudin-PDZD8 system is also essential for the establishment of neuronal polarity. Our results suggest that protrudin and PDZD8 cooperatively promote endosome maturation by mediating ER-LyLE tethering and lipid extraction at MCSs, thereby maintaining neuronal polarity and integrity.

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